Antenna



L. J. CHU

ANTENNA Filed July 9, 1945 5555555500' Lf/ 70a @Jaaa 7 1 JJU M- wwf/MMcv/ INVENTOR LAN JEN. CHU

ATTORN EY Patented ug. 16,V 1949 Y Y z ,r'zazoa` Y Y y Lan J en Chu,Brookline, Mass., assigner, by mesne ssignm'ents,"t`o` tlieUnited Statesof America as1represcnted.by.the Secretary of l f Aereaengage.er

eclaimsv.. (C1150- salem This invention relates "to antenna andmoreparticipara to' ritenne adapte@ for lise win; highAfrequency'communication systeins.' i"

'Figfl illustrates-orie embodiment of theinvention; and; l. A

Fig'.- l2l illustrates-a preferred. embodiment-ofthe invention.-

Fig.- 3`-illustrates a sectional Aview takenv alongV line-S-ofiig. l;anda Fig. 4-illustrates yal sectional-,view taken: along1ine.4-4ioff.fFig.1.u" M u Rectangular wave guide 5 has apluralitylloffr apertures y'82preferably in one narrow wall 6 thereof,these apertures being` spaced apart a distance a whichisYsubst'aritially equal to a wavelengthinrthe jguide,r and .is.terminatedbytanf adjustable'plunger 1. Parallel plat'elwaveguidefComprisinewo, .coniugare .,paalllel-plaii filetes ID and I,"extendsgenerally normal to the wall E of lwave guide 5 in whichithe aperture8lare provided.y Y f waveguide. 9. restricts remedied@ fregi @l2-11.-tures 8 to the spa`ce betwe n itsuplates I0 and IIJ', that is, generallyspeaking; to a plane normal to Wave guide 9 is terminated by a movableplunger.; I I along the side opposed to apertures 8. As will be apparentfrom the explanation to follow, the other two sides I'2 and I3 of waveguide 9 may be closed or not, as desired.

One plate I of wave guide 9 has a plurality of apertures I4 thereinspaced apart a distance b corresponding to the wavelength in wave guide9, which may be the same as the free space wavelength at the frequencycontemplated.V

If energy is directed into wave guide in the direction of plunger 1,part of the energy will leak or escape through apertures 8. Plunger 1may be faced with energy-absorbent material, or have a reflectingsurface, and is adjusted to reduce the standing wave ratio to a minimumin wave guide 5. As shown in Fig. 3, plunger I m'oves Within Wave guide5 in the direction of the arrow. T0 make a desired adjustment, set screw3D is moved, in the direction of the arrow, Within slotted portion 3I ofwave guide 5. It is preferred that distance a approach the free spacewave length, and in any event since energy escaping from apertures 8 isin phase, the major portion of the energy will be directed normally tothe wall 6 containing apertures 8.- Thus', it'willbe seen that-itis notnecessary'to haveslde walls" I2 arid vI3 to'fvvaveV- gli eS althoughth'es may 'be'inclded toiinini? iriiaethe fescapel'f( energy conta 1 alongitudinal central line alongA bfad waIlI Therefore?prtrs'* |15 mairiepcdfrom apertures lrrby a distance a substantially a half wave length inthe wave guide I5 at the frequency involved, and by staggering aperturesI1 and I8 on opposite sides of the longitudinal median line of broadwall I5, radiation from al1 the apertures will be in phase. A parallelplate Wave guide I9 having plates 2D and 2D may be extended generallynormal to broad wall I5 in a manner similar to that in which parallelplate wave guide 9 extends normally to narrow wall 6 of wave guide 5in'Fig. 1. In one plate 20 of wave guide I9 of Fig. 2 are an array ofapertures 2! and 22 aligned with apertures I1 and I8 respectively, andalso spaced apart a distance a in the direction parallel to broad wallI6. In the direction normal to broad wall I6 they may be spaced apart adistance b substantially equal to one Wave length in free space. Thus anarrow directed pencil beam will extend normally to plate 20 containingapertures 2I and 22.

A further improvement may be obtained Vby reducing the distance b' (orb) to a value less than the free space wavelength, even though slightlyless, which will result in materially reducing side lobes. The radiationthen will not be normal to plate 20, but Will still be a pencil, ordirected beam, with side lobes reduced. Although not shown in Fig. 2,adjustable plungers may be used in a manner similar to that in whichthey are employed in the device shown in Fig. 1 in order to reducestanding Waves Within wave guides I5 and I9.

As is Well known in the art, antennas having directive effects inradiation conversely have like directive effects in reception andsimilar structures may be used for radiation or reception ofelectromagnetic energy.

Many variations will be apparent to those skilled in the art, andtherefore it is not desired to restrict the scope of the invention tothe precise embodiment herein disclosed.

What is claimed is:

1.' In combination, a rectangular Wave guide having apertures along oneWall thereof spaced at equal intervals of substantially one Wavelengthin the guide at the operating frequency, and a parallel plate Wave guidewhose plates eX- tend substantially normal from said one Wall, one ofsaid plates having openings therein in alignment in a direction normalto said one Wall with the apertures in said one Wall and spaced apartsubstantially one free-space Wavelength at the operating frequency inthe direction normal to said one Wall, whereby a pencil beam ofelectromagnetic energy may be radiated into space from said parallelplate Wave guide in a direction normal to the said one plate.

2. The combination of claim 1, including an adjustable plungertermination in said rectangular Wave guide and an adjustable plungertermination in said parallel plate Wave guide.

3. In combination a rectangular wave guide having apertures equallyspaced along one wall thereof, and a parallel plate wave guide havingplates which extend substantially normal from said one Wall, one of saidplates having openings in alignment in a direction normal to said Wallwith said apertures, said openings being also aligned in a directionparallel to said Wall, and spaced apart equally in a direction normal tosaid Wall, whereby a pencil beam of electromagnetic energy may beradiated into space from said openings.

4. The combination of claim 3 including an adjustable plungertermination in said rectangular Wave guide and an adjustable plungertermination in said parallel plate Wave guide.

5. A directive antenna comprising a rst rectangular wave guide havingapertures along one Wall thereof spaced at equal intervals ofsubstantially one half Wave length in the guide at the operatingfrequency, said apertures being staggered on opposite sides of thelongitudinal median line of said Wall, and a parallel plate Wave guideWhose plates extend substantially normal from said one Wall, one of saidplates having openings therein in alignment in a direction normal tosaid one Wall with the apertures in said one Wall and spaced apart inthe direction parallel to said one Wall at intervals equal to those ofthe apertures in said one Wall, said plate openings being spaced apartin the direction normal to said one Wall at equal intervals ofsubstantially one wave length in free space at the operating frequency.

6: VA directive antenna comprising a rst rectangular wave guide, one ofthe walls thereof having a plurality of equally spaced apertures formedtherein, said apertures being staggered on opposite sides of thelongitudinal median line of said Wall, and a second Wave guide includingtwo parallel plates normal to said apertured Wall and enclosingsaid-apertures, one of said enclosing plates having apertures therein inalignment in a direction normal to said one Wall with the apertures insaid one wall and spaced apart in the direction parallel to said oneWall at intervals equal to those of the apertures in said one wall, saidplate apertures being spaced apart at predetermined intervals in thedirection normal to said one Wall.

LAN JEN CHU.

REFERENCES CITED The following references are of record in the iile ofthis patent:

UNITED STATES PATENTS Number Name Date 2,226,479 Pupp Dec. 24, 19402,297,202 Dallenbach Sept. 29, 1942 OTHER REFERENCES Ser. No. 353,755,Dallenbach (A. P. C.) pub. May 25, 1943.

